Staircase step



FIG. 1 is a top perspective view of the staircase step showing my new design;

FIG. 2 is a bottom perspective view thereof;

FIG. 3 is a side perspective view thereof;

FIG. 4 is a side view thereof;

FIG. 5 is a front view thereof, shown in a larger scale; and,

FIG. 6 is a back view thereof, shown in a larger scale. 

CLAIM The ornamental design for a staircase step, as shown and described. 